Ceramic space heater



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l CERAMIC SPACE HEATER- Filed May 30. 1944 I v 7 Sheets-Sheet 5 Sept. 6,1949. G. A. BoLE ETAL' 2,481,069

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721 @o a? .a9 l :1.90 La Sept., 6, w49..y G. A. BOLE E-r AL 2,48159CERAMIC SPAQE HEATER Filed May 30, 1944 7 Sheetsl--Sheetv '7 PatentedlSept. 6, 13949 CERAMIC SPACE HEATER George A. Bole and DeWitt H. Wyatt,Columbus, Ohio, assignors to The Ohio State University ResearchFoundation, Columbus, Ohio, a corporation of Ohio Application May 30,1944, Serial No. 538,035

8 Claims.

This invention relates to fuel-burning appliances, and has particularreference to room heaters, stoves and furnaces employed in the heatingof residences and other buildings.

Usually, such appliances are formed primarily from metal for conveniencein fabrication and since metal is a good heat-conducting material.However, metal stoves are highly sensitive to combustion taking placetherein and quickly cool off, causing room areas heated thereby toreadily vary in temperature. Ceramic materials, on the other hand, donot possess the same high rate of heat conductivity as metal, but whenonce heated, the same retain their heat to a materially greater extentthan metal and, as a result, provide a more uniform heating temperaturefor longer periods of time than can be obtained with the use of metal.Furthermore, with the present relative scarcity of metals, we have foundceramic materials well suited for stove design, providing that adequateprovision is made for the proper circulation or passage of air overheated surfaces.

It is, therefore, one of the principal objects of the present inventionto provide an efficient, durable and low-cost heater, stove or furnaceadapted particularly, though not necessarily so limited, for thecombustion of solid fuels, and wherein the wall-forming members of theheater or stove casing are composed primarily of materials having aceramic composition, using but minimum amounts of metal in theconstruction thereof.

It is another object of the invention to provide a fuel-burning heaterhaving a ceramic casing and provided internally with a fuel-magazine ofstorage capacity, whereby fuel is fed gravitationally toward a grate orhigh temperature zone of combustion, passages being so formed in thewalls of the casing as to provide adequate draft through thefuel-containing magazine, causing fuel gases or volatiles to 4bethoroughly burned and consumed, thereby increasing the efficiency to thestove or heater and eliminating, or substantially reducing, theformation of soot and smoke.

Another object of the invention is to provide a heater of the characterindicated, wherein the ceramic casing thereof is formed with passages ofnovel design adapted for the extended passage of the hot flue gasesgenerated by fuel combustion within the casing, so that the contact ofsaid gases with the heat-liberating surfaces of the casing will besufficiently prolonged to provide for efficient heat transfer andresulting low temperatures in the out-flowing chimney gases.

A further object is to provide the -ceramic casing of such afuel-burning stove or heater with additional passages, spaced from theue gas passages, for the circulation of room air, whereby when the stoveis utilized as a space heater,

an efficient interchange of heat is obtainable.'

A license to this invention or any patent or patents which maybe issuedthereon, based upon disclosures in this application, is granted to theGovernment of the United States.

Other objects and advantages will be apparent from consideration of thefollowing description and the accompanying drawings, wherein:

Fig. 1 is a perspective view of a ceramic heater formed in accordancewith the present invention;

Fig. 2 is a similar view, on a somewhat reduced scale, looking towardthe rear of the heater;

Fig. 3 is a perspective view, showing the various parts of the heater ina separated state, parts of the heater casing being .broken away todisclose internal structure;

Fig. 4 is a vertical sectional view taken through the heater;

Fig. 5 is a horizontal sectional view taken on the plane indicated bythe line V--V of Fig, 4;

Fig. 6 is a fragmentary vertical sectional View on the plane indicatedby the line VI-VI of Fig. 4;

Fig. 7 is a perspective View of the removable ash receiver;

Fig. 8 is a detail vertical sectional view taken through the ashreceiver;

Fig. 9 is a transverse sectional view on the line IX--IX of Fig. 8;

Fig. 10 is asimilar View on the plane indicated by the line X-X of Fig.8;

Fig. l1 is a detail vertical sectional View disclosing the damper andby-pass valve operating mechanisms;

Fig. 12 is a sectional View on the line XII-XII of Fig. l1;

Fig. 13 is a detail vertical sectional view disclosing the butterflyvalve operating means;

Fig. 14 is a bottom plan view of the removable cover section of theheater;

Fig. l5 is a top plan view thereof;

Fig. 16 is a perspective view of one of the bowl-forming refractories;

Fig. 17 is a similar view of one of the grid elements.

Referring more particularly to the drawings, the numeral I0 designatesthe base section of our improved heater. The same comprises a firedclaybody having a horizontal bottom wall i I, integral upwardly extendinginner walls I2 and a vertical outer wall I3, the walls I2 and i3 beingspaced as at Ill. The upper portion of the inner walls I2 terminatebelow the upper edges of the outer walls I3 to provide horizontallydisposed ledges I5, the latter being adapted to receive and support asheet metal grate plate I6.

At its front, the base section is formed with an ash pit opening Ilwhich is adapted to be at least partially closed by a draft door I8.This door is also formed from ceramic materials and is provided withspaced ports. i9 disposed and proportioned to provide for the inovv ofroom air into the ash pit 28 of the base section. The door I8 issupported in the opening l1 by being provided at its lower and innersides with integral inwardly projecting ears 2i which are diagonallyslotted as at 22 for the reception of stationary pivot pins 23, thelatter projecting horiiontally from the sides of the opening I1. Thedoor' swing about the axis afforded by the pins 23, but also may beadjusted relatively thereto by the provision of the slots 22. The top ofthe door at its inner side is provided with a spaced pairl of lugs 26,which carry latch pins 25. When the door is closed, as in Fig'. 4, theends. of these pins engage with, shoulders 25. on the grate plate i6which maintain the door in a substantially vertical positiorL The outerwalls i3, of the base section may, at the, sides and back thereof, beprovided with oor recesses, 25 by which air, withdrawn from. the flooron which thev heater isv positioned,l is introduced into vertical`passages 2l formed in the corners of said base section between the innerand outer walls l2 and I3. The grate plate I6 has its corners nerturedas. at 2.3 for registration with the upper ends. of thepassages 21, asshown in Fig. 3.. Also, the front` of the grate plate has formed thereina rectangular slot 29 in which is positioned a pivotally movablebutterfly valve 3e, which is employed in controlling the flow of airinto upper portions of the heater casing. Likewise, at its rear, thegrate plate is provided with a rectangular` opening 3i. invvhich. is;located a pivoted airflow-.controlling valve 3.2, the operation of whichwill. be hereinafter described..

Centrally, the plate i6. is formed With a gratereceiving opening 33 andbelow this opening with a, depending iiange 3A.. Supported on. thislangeis a metallic spider 35 upon which is positioned a perlorate, circularceramic grate 3,6.. The grate is formed from a molded body ot ceramicycomposition and. is. provided. centrally with communicating radiallydisposed passages. 31.1 which extend tbrQugh. they grate from., top tobottom thereof, said passages providing. for the flowv of air centrallythrough` the grate in an upward direction in Contact. with the extendedsurfacev area et the grate body. The air so supplied is used for thedual purpose. of contributing to the. active comjbustion of fuel burnedover the grate and also to cool and,A maintain the grate at operatingtemperatures of-l such. order that the composition. of the grate` will.not be. deleteriously affected by the temperatures to which. it4 is-ysubjected during operation of the. heater..

Thebottom of thezgrate is formed with grooves 38 which receive thesupporting spider 35. Preferably the top of the grate iso conical.formation to provide for the gravitational passage ot burning fuelsthereoyer in an outward, peripheral direction. |Ijhe diameter ot thegrate yis such. that it is spaced from the edge Wallsof the opening.l33., in order that., the fine ash, produced throughi theoperation of.the heater, may gravitate` down-- Wardly into4 the pit 20, Where; in,the preferred form of our invention, a removable ash receiver 39,. islocated.

Theash receiver comprisesa circula-r outer casing, 4D, which is formed peripherally with a lever housing 4 l, theinterior ofthecasinggbeing.formed to. provide an. ash-receivingwell. 42. Rivet-ally mounted, as at43, withinthe; housingI LL is.- an operating lever 4 4, the-latter;extending; throughan arcuateslot deformed inthe-,housingand terminatingatrits outer end in a manipulating eXtension 46. A spring. 41 has oneend fixed within the housing lll and the other end receivable in arecess d8 formed in one edge of the widened inncr end of the lever.Also, pivotally connected as at le with the inner end of the lever isone end of a link et, the opposite end of said link being pivoted as at5i to astationary support 52 which is disposed longitudinal-ly in theopen bottom of the housing and. which normally rests on the uppersurface of the bottom wall l l of the base section iil. United' with thepivot 49 of the lever is a barv 53 the forward end of this bar beingpivoted as at 54 to a pair of diverging links 55. The lower of theselinks are pivoted, as at 56, to the support 52; while the upper oi thelinks 55y are pivoted, as at. 5,1, to the housing 4l. In the axialcenter of. the casing ll-S, they support 5211s equipped with a dependingdisk 58 which is received in a centering and stop. socket. 59, providedin the wall il of the base section. The upper perimeter of the casingdo. includes. a plurality of spaced upstanding lugs lill. which, receivebetween them the radiating wires constituting. the spider 35 when thecasing 4@ is elevated. Such elevation is accomplished by depressing theouter end of the lever lllwhich results in longitudinally moving the bar5.3 in a horizontal plane toward the center of the casing, causingeleva-tion of the links. 5l! and 55 and thereby bodily raising thecasing lil until, itsperipheral ilange Ei i engages with, the flange- 34on which the spider` 35. is rotatably positioned.

This engagement shuts off the now of primary air passing through thegrate opening to the bottom of the grate 35. and mechanically unites theash. receiver with the grate. By grasping the housing extension 4l ofthe casing, the grate may then be oscillated about its verticalv axis,causing the fine. ash` to, pass4 through the opening 33 and i into, theWell d2. of the ash receiver. When lled on the upper surface of thegrate plate I5 are the lower edges. of the intermediate section of theheater casing. As shown in Fig. 5, the intermediate section comprises aceramic body substantially rectangular in its horizontal cross section,the: same, havingspaced inner and outer vertically, extending Wallsl 63-and 64, respectively, these walls being united atV intervals bytransversely extending. webs 65. The cross-sectional configuration otthisv intermediate section is such as to` permit ot its extrusionthrough suitable dies, although it may. beformed in any other convenientmanner, as by individually molding the same; At itsfgour corners, theintermediate section. is provided between the, walls 63; 6'4 and 65'with vertical passages 66 which register at their lower. ends with' the.passages 2:1 provided in the basesection landi through which air drawnfrom.l the door beneath; the heater passes upwardly. and is' heated.principally by convection, for discharge into the. room atmosphere.

Between the passages d6; the intermediate casing,l sectionis; formed to.provide vertical flue gas passages, .indicated at 6.1:, 63; and 691 Saidintermediate. section alsoincludes another verticallyextending'arpassage 1.9: between.y convection passages; Q5; and:disposed.. in registration with the front. oilv the; intermediatesection. The passage 10i has;v its lon/.erf end disposed over and inregistration with. the'. sl'ot 292 and; butterflyI valve 3U of the`grate. plate; I; so. that. Wheny the valvev 30 is open, air, enteringthe front part of the ash pit 20, will be diverted in part and caused totraverse the passage lil in an upward direction, for a purpose to behereinafter explained.

Positioned on the upper edges of the intermediate casing section is amineral fiber or other gasket 'l l, and mounted on the upper surface ofthis gasket is a metallic top plate l2. Centrally, the plate l2 isprovided with a magazine opening from the margins of which depend ametallic cylinder i3 which is slotted vertically as at I4 to provide gasoutlets. Seated on the upper surfaces of the plate l2 is the top section'l5 of the heater casing, said top section being of ceramic compositionand formed with an outer flange 16 which is shouldered as at ll toengage the plate 'i2 and the gasket l l. Centrally, the top sectionincludes a depending fuel-receiving throat 18, the latter beingdispo-sed in registration with the upper end of the cylinder 'I3 to formthe upper part of a fuel magazine. The upper end of the throat is closedby a removable ceramic lid 19. This lid seats in a recess Se provided inthe upper end of the throat l, the recess being formed at intervals withupstanding lugs 8| which are receivable in grooves d?, provided in theunder part of the lid, so that when the lugs are disposed in the grooves32, the lid will be fully seated within the recess 30. However, when thelid is rotated so that the grooves do not register with the lugs, thesame will be slightly elevated to admit air into the upper part of thefuel-containing magazine.

Mounted on the grate plate structure I6 and surrounding the grate 3d isa plurality of circularly disposed segmental refractcries 83. As thecoal gravitationally descends in the fuel magazine, the temperaturethereof increases, gases and volatiles being released from the coal asthe temperature thereof progressively increases and by the time the fuelreaches the lower part of the combustion bowl, provided by therefractories 83, it is usually in the form of burning coke. The lowerportion of the refractories 33 provide inwardly sloping surfaces edwhich direct the fuel toward the upper conical end of the grate 36. Inaddition to being slightly spaced relative to each other to form slotsor grooves therebeteween, the refractories are provided, contiguous totheir upper ends, with widened ledges 85 in which are formed gas outletsB6. The high temperature gases issuing from the outlets 85% impinge theinner surfaces of the casing walls Erl and sweep upwardly through thespace or spaces 8l formed within the casing and which communicate with aflue gas chamber 88 provided in the upper portion of the intermediatesection of the casing. The flue gas space 8'! and the chamber 88 areseparated by a ceramic baffle plate 89 which is positioned on shoulders90 provided on the walls 50..

The bailie plate 89 is formed with openings 9| through which extend aplurality of secondary air-conducting tubes 92. These tubes arevertically arranged with their lo-wer ends resting on the ledges 3'5 ofthe refractories 83 and the upper open ends of said tubes register withcorresponding openings provided in the top plate structure l2, in orderthat by means of chambers 93, provided in the under part of the lid '19,the said tubes will receive downwardly moving air which has beenintroduced into the casing through the passage 10. In the lengththereof, below the cylinder lf3, the tubes are provided with inwardlydirected, vertically spaced ports 94 by which inwardly-directed 2 fsecondary air may enter the vertically disposed column of fuel in themagazine as the fuel approaches the coke-forming zone. The introductionof this secondary air serves to provide for active combustion of gasesor volatiles released from the fuel during distillation thereof, andthese burning gases or volatiles are withdrawn from the magazine bypassing through the interstices 95 formed between a plurality of ceramicgrid elements $6.` These grid elements, in their preferred form, areeach of generally arcuate configuration and are disposed in superposedorder in vertical rows. The ends of each of the elements are arcuatelyformed, as at 91, to engage with the outer rounded surfaces of the tubes92. Also, the innerwalls 64 are provided with vertically disposed ribsv98 which engage with the ends of the elements 96 and maintain thelatter in their proper relative order. Also, the grid elements areformed with beveled adjacent surfaces 99 which produce the slots orinterstices 95 between the same and through which the released fuelgases may travel when passing from the magazine proper into the space orspaces 81.

The vertical flue gas passages B1, E8 and 69, formed in the intermediatesection of the casing, are provided contiguous to their lower portionswith openings |03 by which a portion of the flue gases delivered to thespace or spaces 8! are transferred to and pass upwardly through saidlast-named passages and are received in the chamber 88. 'I'he heat ofthese gases is transferred in large part to the walls G3, 64 and 65,heating the air traveling through the passages 66. The upper ends of thepassages G communicate with chambers 7|0|, provided in the under .partof the lid 15, and issue into the room by way of the louvered outlets|02, integrally formed with the lid. Communicating with the chamber 88,and positioned in an opening |03 provided in the rear of the walls 63 isa furnace gas outlet housing |04. Thishousing is provided with an eX-tension |05 which is adapted for connection with a chimney or other gasoutlet stack, not shown.

To control the operation of the damper valve 32, provided in the bottomof the check draft passageway 68, use is made of a vertically extendingrod |06 which, at its lower end, is engaged with an eccentric ear |07provided on the valve, so that as the rod |06 is raised or lowered, thevalve 32 may be turned about its pivotal mounting to open or close theopening 3| in the grate plate structure I6. The rod |06 is locatedvertically in the length of the passageway 68, and at its upper end hasthreaded engagement with an adjustable bearing sleeve |08. Said sleeveis formed with V-shaped lower surfaces |09 which have edge bearing onthe bifurcated arms 0 of a counterbalancing lever This lever is pivotedas at 2 in connection with the walls of the housing |04, and, at oneend, the lever is weighted, as at H3, to offset the weight of associatedstructure influenced thereby, the tendency of the weighted end of thelever being to elevate the rod |06 to close the damper valve 32.

The upper end of the sleeve |08 is maintained by the lever in engagementwith a horizontally disposed lug ||4 formed on one o-f a pair of armsVH5. These arms are pivoted as at H8 to the housing |04 and project intothe chamber 88. At their inner ends, the arms are provided with pinsreceivable in slots ||8 formed in the upper ends of links ||9. The lowerends of the links are connected with ceramic bypass valves,

insertion of a poker or the like into the magazine to break up such fuelbridging or fusion.

The parts of the heater are of sturdy and rugged construction, fullycapable of withstand ing without injury, for sustained periods of use,the temperatures present within the heater, In the event of mechanicalfailure, however, defective parts may be readily replaced at low costs.

While the intermediate section of the casing has been shown ascomprising an integral unin tary structure, nevertheless, if desired,the same may be composed of two or more parts. It will be understoodthat the composition of the ceramic parts used in the construction ofour irnproved heater is such that it will highly resist cracking,spalling or other forms of deterioration attributable to hightemperatures, or to the tem perature gradient set up in the outercasing. Also, while we prefer to form the parts of the heater primarilyfrom ceramic materials, never f theless, it will be appreciated that themechanical features of the heater, by which improved fuel combustion andheat exchange take place, lend themselves to the use of other materials,such as sheet or cast metal, and with respect to these features, we donot limit ourselves to the employment of ceramic materials alone. Whilethe heater has been particularly designed for the burning of solidfuels, such as various grades of coal, it is within the scope of theinvention to produce heat by the burning of gas or oil, in which case aceramic rubble may be placed in the combustion space or fuel magazine,thus enabling the apparatus to function as a storage heater.

We claim:

l. A solid fuel burning heater, comprising a casing of ceramiccomposition, composed of a base section formed with an air-admitting ashpit, a separable intermediate section having an internal fuel magazinepositioned on said base section, said intermediate section being formedto provide spaced inner and outer vertically extending parallel wallsintegrally united at intervals by transverse walls, said walls formingtherebetween open-ended heat interchanging passages consisting of: rst,a passage for the travel of air used in fuel combustion, second, a fluegas passage, third, a plurality of air-heating passages and, fourth, acheck draft passage,

said combustion air passage being in communication at its lower end withthe atmosphere of said ash pit and at its upper end with said fuelmagazine, said ue gas passage being provided adjacent to its lower endwith a flue gas inlet and at its upper end with a flue gas outlet, saidair-heating passages at their lower and upper ends being incommunication with the atmosphere, and said draft passage at its lowerend being in communication with the atmosphere of said ash pit andhaving a ilus gas inlet adjacent its lower region and a flue gas outletat its upper end, a separable top section seated on the upper portion ofsaid intermediate section, fire bowl refractories providing a hightemperature combustion zone stationarily disposed in the bottom of thefuel magazine provided centrally in the intermediate section, saidrefractories being spaced from the inner walls of the intermediatesection to provide a flue gas space therebetween with which space theinlet openings in the lower portions of the fiue gas and draft passagesare in open communication, and a grate supported between said ash pitand said high temperature combustion zone.

2. A heater as defined in claim 1 and wherein the grate is of ceramicconstruction having air passageways formed therein for the transmissionof primary combustion air from the atmosphere of the ash pit to the hightemperature combustion zone.

3. A heater for burning solid fuels comprising a casing of ceramiccomposition, said casing embodying a base section formed with anair-admitting ash pit, a separable intermediate section having aninternal fuelreceiving magazine positioned on said base section, saidintermediate section providing spaced inner and outer verticallyextending parallel walls integrally united at intervals by transversewalls, said walls forming therebetween open-ended heat exchangingpassages, the latter embodying: first, a passage for the travel of airused in fuel combustion, second, a ue gas passage, third, a plurality ofair-heating passages and, fourth, a check draft passage, said combustionair passage being in communication at its lower end with the atmosphereof said ash pit and at its upper end with said magazine, said flue gaspassage being provided adjacent its lower end with a flue gas openingand at its upper end with a flue gas outlet, said air-heating passagesat their lower ends being in communication with continuing andregistering open-ended passages formed in said base section, and saiddraft passage at its lower end being in communication with theatmosphere of said ash pit and having an outlet at its upper end, and aseparable top section seated on the upper portion of said intermediatesection, said top section being provided with spaced internal chambers,one of said chambers communicating with said combustion air passage todirect air discharged therefrom to said magazine and the other of saidchambers communicating and with the upper ends of said airheatingpassages for delivery to the atmosphere through vents in the walls ofthe last-named chamber.

4. A fuel-burning heater as defined in claim 3 having a verticallydisposed fuel-receiving magazine provided centrally in the intermediateand top sections, and a grate structure provided in the bottom of saidmagazine.

5. A solid fuel-burning heater, comprising a casing of ceramiccomposition embodying a base section formed with an air admitting ashpit, a separable intermediate section having an internal fuel magazinepositioned on said base section, said intermediate section being formedto provide spaced inner and outer vertically extending parallel wallsunited at intervals by transverse walls, said walls forming therebetweenfor heat interchange, first, a passage for the travel of air used infuel combustion, second, a flue gas passage, third, a plurality ofair-heating passages and, fourth, a check draft passage, said combustionair passage being in communication at its lower end with the atmosphereof said ash pit, said flue gas passage being provided adjacent to itslower region with a flue gas inlet and in its upper region with a fluegas outlet, said air-heating passages at their lower ends being incommunication with complemental open-ended passages formed in said basesection, and said draft passage at its lower end being in communicationwith the atmosphere of said ash pit and having a flue gas inlet adjacentto its lower region and an outlet therefor at its upper end, a separabletop section seated on the upper portion of said intermediate section, atop plate arranged between said intermediate and top sections, portedfire bowl refrac- 11 tores stationarily disposed in the bottom of a fuelmagazine provided centrally in the intermediate and top sections, saidrefractories being spaced from the inner walls of` the intermediatesection to provide a flue gas space therebetween with which space theinlet openings in the lower portions of the flue gas and draft passagesare in open communication, a horizontally disposed baffle memberstationarily positioned in said intermediate section below the flue gasoutlets in the upper regions of said flue gas and draft passages, saidmember being formed with valve openings and normally closing the upperregions of the nue gas space, there being a nue gas outlet chamberformed with an outlet passage provided in said intermediate sectionabove said baiiie and below said top plate, said chamber being incommunication with the upper portions of the gas and draft passages bythe outlets provided therein, said chamber further communicationg bysaid outlet passage with the atmosphere, a grate plate arrangedhorizontally between said base and intermediate sections, said,y grate`plate being formed with openings establishing communication between theair heating passages provided in the base and intermediate sections andbeing further provided with openings establishing communication betweenthe ash pit of said base section and said combustion air and draftpassages, movable valves positioned in said last-named openings forcontrolling the ow of air from said ash pit into said combustion air anddraft passages, by-pass valves normally closing the valve openingsformed in said baie member, said by-pass valves, when open, establishinga by-pass for the flue gas from the normally closed upper regions ofsaid ue gas space directly into said flue gas chamber, a plurality ofportedy airconducting tubes disposed at' the' sides of said fuelmagazine and above said bowl refractories, said tubes at their upperends being in communication with a chamber provided in said topsectionand openings in said top plate with which the upper end of saidcombustion air passage communicates, a plurality of grid elementspositioned at the sides of said magazine in abutting` relationship withsaid tubes, said elements forming between them a multiplicity ofin-terstices providing for gas now between said magazinel and flue gasspace, and a rotary ceramic gratev element carried by said grate platein the-bottom of said fuel magazine, the upperv portion of said gra-teelement being surrounded by said bowl refractories.

6. A solid fuel-burning heater` comprising? a casing of ceramiccomposition, the bottom of said casing being formed with an air-ventedVash pit and centrally above said ashl pit with a fuelreceiving magazinecoextensive with the height of the casing, a ceramic gra-te providedwith air passages supported by said casing between said ash pit and thebottom of said fuel magazine, re bowl refractories positioned in thebottom of said fuel magazine surrounding said grate to form a hightemperature fuel combustion zone, the walls of said casing embodyingspaced` vertically extending inner and outer members,- integrally unitedby transverse webs and forming a fiue gas passage leading from said hightemperat'ure combustion zone to, an atmosphere vented flue gas chamberdisposed inthe upper portion of said casing, said casing wallsadditionally providing aV check draft passage, the latter communicatingat its lower end with said ash pit and at its upper end withsaid fluegas chamber, and a manually controlled damper valve for governing airflow from said ash pit into said draft passage.

7. A heater for burning solid fuels comprising a casing having aninternal vertically and Centrally arranged fuel-receiving magazine, thebottom of said casing being formed below said magazine with anatmosphere-vented ash pit, a movable grate arranged between the ash pitand the lower part of the fuel magazine, a plurality of blockrefractories arranged in the bottom of said magazine. around said gratetoy form a fire bowl providing for active combustion of fuel deliveredthereto from the magazine, a plurality of relatively spaced grid-formingrefractories positioned on the top of said block refractories, verticalair-supplying tubes arranged at the sides of said magazine above saidblock refractories, said tubes being formed with ports locatedimmediately adjacent to grid-forming refractories, the outer walls ofsaid casing being formed With a vertically extending open-ended passage,the lower end of said passage being in communication with said ash pitand the upper end thereof in communication with the upper ends of saidair-supplying tubes, manually adjustable valve means for regulating theflow of air from said ash pit into said passage, and a flue-gas passageformed in the walls of said casing, said gas passage having an inlet incomm-unication with a zone of active fuel combustion adjacent to saidblock refractories and an outlet in communication with the atmosphere.

8. A heater for burning solid fuels comprising, a casing formedinternally with a vertically extending centrally disposed uel-receivingmagazine and an underlying ash pit, the letter being vented to theatmosphere, the walls in the upper portion of said casing being arrangedto form a fiue gas outlet chamber, a flue gas passage formed in theWalls of said chamber leading from the bottom of said fuel magazine tosaid chamber, a check draft passage formed in the walls of said casing,the lower end of said draft passage being in communication with said ashpit andthe upper end thereof with said chamber, and valve means forregulating volumetzicaliy the flow of air through said draft passage andfrom said ash pit.

GEORGE A. BOLE.

DE WITT H. WYAT'I'.

REFERENCES CITED The following references are of record in the file ofthis lpatent:

UNITED STATES PATENTS Number Name Date 119,719 Rand Oct. 10, 1871285,397 Dodge Sept. 25, 1883 434,403 Rube Aug. 12, 1893 1,322,425 GareyNov. 18, 1919 1,987,548 Brooks Jan. 8, 1935 2,367,094 Blumstengel Jan.9, 1945 FOREIGN PATENTS Number Country Date 2,133 Sweden Apr. 20, 188911,872 Germany Nov. 19, 1880 17,682 Great Britain 1898 89,334 GermanyDec. 17, 1895 128,472 Great Britain June 26, 1919 152,307 Germany June10, 1904 196,632 Great Britain July 4, 1924 760,502 France July l, 1934

